Wheels and tires for vehicles as manufactured typically are not rotationally balanced. When a tire is mounted on a wheel and placed in service on a vehicle, rotational imbalance can result in undue vibration in the vehicle and rapid wear on the mounted tire leading to premature failure. Therefore, it is common practice to dynamically balance each mounted tire, either before or after installation on the vehicle, before the tire is placed in road service.
In the prior art as commonly practiced today, the mounted tire is mounted on a machine that determines through rotation both the degree of imbalance and the radial (also referred to herein equivalently as “azimuthal”) location of the maximum imbalance. A technician then attaches one or more appropriate weights to the rim flange of the wheel at a point generally opposite from the maximum imbalance. Sometimes, the weight is divided between the inner rim flange and the outer rim flange of the wheel, or it may be installed entirely on the inner rim for cosmetic purposes.
This prior art method results in the mounted tire having a center of rotation that coincides with the axis of rotation of the vehicle axis. However, a source of imbalance still exists because the weights are not necessarily disposed in the central plane of mass of the mounted tire, perpendicular to the axis of rotation, placing a wobble tendency on the wheel bearings and resulting in a residual low level of rotational vibration. The prior art method can vary only the angular position of the weight and the amount of weight used. It cannot also vary the weight's position in the direction parallel to the wheel's axis of rotation (longitudinal), which is necessary to place the weights in the plane of central mass to eliminate this additional source of vibration and tire wear.
What is needed in the art is a method and apparatus wherein the balancing weight for a mounted tire is correctly disposed both azimuthally and longitudinally of the mounted tire.
It is a principal object of the present invention to eliminate both azimuthal and longitudinal vibrations in a mounted tire in road service on a vehicle.
It is a further object of the invention to increase the working mileage of a tire.
It is a still further object of the invention to improve the riding comfort of occupants of a vehicle.